1. Field of the Invention
The present invention relates to a paper feeder configured to store in a storage section thereof a plurality of sheet members to be feed to a processing apparatus configured to perform processing on such sheet members, the paper feeder having a feed path for transporting the sheet members from the storage section to the processing apparatus.
2. Description of the Related Art
An image forming apparatus is one example of a processing apparatus configured to perform processing on sheet members, such as recording sheets, fed from a paper feeder. In recent years, such image forming apparatus have progressed toward increases in multifunction capability and in printing speed. For example, an image forming apparatus has been developed which has plural processing modes including a copier mode, printer mode and FAX mode and exhibits a printing speed of one or more sheets per second. Such a high-speed image forming apparatus calls for a paper feeder capable of feeding a large number of recording sheets. The necessity of such a paper feeder becomes high particularly when the image forming apparatus operates in such a mode as the printer mode or FAX mode which does not necessarily need the presence of the user near the apparatus.
In the FAX mode, in particular, a large-capacity paper feeder is indispensable. This is because where the image forming apparatus accumulates in its memory a large quantity of information received in the absence of the user, for example, during nighttime without performing printing for avoiding running out of recording sheet, the memory of the image forming apparatus is required to have a large capacity and a time loss will occur in later printing of the information accumulated in the memory.
However, even such a large-capacity paper feeder cannot store an unlimited number of recording sheets. Generally, the upper limit of a storable number of recording sheets ranges from about 2,000 to about 4,000. This is because the load to be imposed on the lift-up mechanism increases with increasing number of recording sheets to be stored and, when the number of recording sheets becomes excessive, the lift-up mechanism needs to be made more solid, which will result in increases in the size of the paper feeder and in cost while making it difficult to adjust the height of a stack of recording sheets precisely. The lift-up mechanism is configured to lift up such a recording sheet stack in order to keep the height position of the topmost sheet of the stack held in the paper feeder within a predetermined range, whenever necessary.
In view of this situation, a large-capacity paper feeder to be disposed adjacent to such an image forming apparatus separately from the paper feeder section provided within the image forming apparatus is under development. For example, Japanese Patent Laid-Open Publication No. HEI 5-193766 discloses a paper feeder having plural sheet storage sections vertically arranged in tier for storing an increased number of recording sheets. Each recording sheet fed from this paper feeder is taken into the image forming apparatus through a sheet feed inlet which is continuous with sheet feed path defined in the image forming apparatus. The sheet feed inlet of the image forming apparatus is positioned so as to be continuous with the sheet feed path.
Since the sheet feed inlet of the image forming apparatus is thus positioned so as to be continuous with the sheet feed path for communication, a sheet storage section of the conventional paper feeder which is positioned at a height different from that of the sheet feed inlet defines a bent or curved sheet feed path between the sheet storage section and the sheet feed inlet. For this reason, each recording sheet being fed within the paper feeder is likely to curve due to increasing possibility of folding or bending, which will incur the occurrence of jam during feeding and degradation in print quality.
A feature of the present invention is to provide a paper feeder which is capable of feeding a large number of sheet members such as recording sheets while preventing such sheet members from curving, hence, from jamming during feeding.